1. Field of the Invention
This invention lies in the field of burner systems for the combustion of gaseous or liquid fuel. More particularly, it concerns a type of burner system in which the combustion air can be directed past the burners into the combustion zone in either a completely axial direction of flow, or a completely helical direction of flow, or in some combination of axial and helical flow.
2. Description of the Prior Art
In the practice of fuel burning for a required heat release, as in now common to the fuel burning arts, it is necessary, at times and for well-known reasons to cause the air flow through the burner, for supply of oxygen to permit combustion, to be tangential in relation to the circular opening (spinning air) up to the area in which combustion is to occur. The circular opening discharges air and fuel forwardly into the furnace which is being fired.
The required amount of tangential (spinning) air movement is imparted to the air as it enters the burner structure, due to lower pressure within the burner than the pressure at which air is supplied up to the burner, or, because of air pressure drop from supply pressure to the pressure within the burner, and the furnace, which is downstream from the burner. The amount of spin is controlled by the angle of tangential vanes.
The cross-sectional area air flow entry is dependent on the chosen orientation of the tangential vanes. As the tangential positions of the vanes are altered, for "spin" control on air flow, the air entry area is correspondingly altered. Increased tangential moment (spin) reduces the air flow cross-sectional area, and decreased tangential moment has an opposite effect. Thus, the air flow pressure drop for air supply will vary greatly, according to the degree of tangential movement which is required to obtain a preferred burning condition.
As an example, and if the air flow area should be reduced to 1/2, for the same air requirement, four-times the air pressure drop would be required from air supply via the air register to the furnace, since air flow quantity will vary as the square root of the pressure drop. This variation in air pressure drop makes automatic control of fuel firing very difficult, but is typical of today's art of fuel burning where a selectively controlled degree of tangential air movement is required.